Faceted reflector for lighting unit

ABSTRACT

A reflector for a lighting unit includes a plurality of discrete reflecting facets which are individually oriented with respect to a light source such that the superposition of the reflected images synthesizes a predetermined lighting pattern. The prescription for making the reflector, by the techniques disclosed herein, involves selecting the number, size, curvature, and location of each facet to produce undistorted reflected images of the light source, the cumulative effect of which produces the desired illumination distribution within prescribed limits. Glare from the lighting unit is substantially eliminated by positioning contiguous facets such that uncontrolled reflecting surfaces are shaded from the light source.

United States Patent Donohue et a1.

[4 1 Oct. 24, 1972 [54] FACETED REFLECTOR FOR LIGHTING UNIT of Mich.

[731 Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Sept. 23, 1970 [21] Appl. No.: 74,563

[52] US. Cl ...240/4l.36, 240/103 R, 350/299 [51] Int. Cl ..F21v 7/09[58] Field of Search ..240/8.2, 41.36, 103 R;

[56] References Cited UNITED STATES PATENTS 2,255,819 9/1941 Salani..240/41.36 2,611,857 9/1952 Coulter ..240/41.36 X 1,535,985 4/1925Clark ..240/41.36 UX 1,726,379 8/1929 Benford ..240/41.36

Primary Examiner-Samuel S. Matthews Assistant Examiner-Fred L. BraunAttorney-J. L. Carpenter, E. J. Biskup and Peter D. Sachtjen [5 7]ABSTRACT A reflector for a lighting unit includes a plurality ofdiscrete reflecting facets which are individually oriented with respectto a light source such that the superposition of the reflected imagessynthesizes a predetermined lighting pattern. The prescription formaking the reflector, by the techniques disclosed herein, involvesselecting the number, size, curvature, and location of each facet toproduce undistorted reflected images of the light source, the cumulativeeffect of which produces the desired illumination distribution withinprescribed limits. Glare from the lighting unit is substantiallyeliminated by positioning contiguous facets such that uncontrolledreflecting surfaces are shaded from the light source.

4 Claims, 20 Drawing Figures Smith ..240/8.2 X

PATENTEH B 24 I972 3.700.883

sum 1 or 5 4LD 3LD ZLD 1D 2RD 3RD 4RD I N VEN TORS ATTORNEY PATENTEU I24 9 3 700 883 sum 3 UF 5 1 N VENTORS ATTORNEY particular, to areflector for a lighting unit such as a motor vehicle lamp assembly.

Conventional motor vehicle lamps of the types used as headlamps,cornering lamps, taillamps, and backup lamps normally include areflector and a lens defining a sealed lamp envelope in which a coiledfilament light source is positioned. The reflector is provided with asuitably curved surface for collecting illumination from the lightsource and redirecting the same outwardly onto the lens. A lightfocusing optical system in the form of dioptic and catadioptric rings,flutes, and prisms is normally provided on the lens for horizontally andvertically distributing the illumination outwardly from the lamp. 5

One of the primary factors afiecting the quality of the projected beamin these lighting units is the ability of the reflector to intercept anddirect toward the lens the light which is emitted from the source. Thiscapability of intercepting source illumination, commonly designated thereflector light collection efficiency, is defined as the fraction oftotal emitted light that is intercepted by the reflector. The collectionefiiciency for a given reflector is dependent on many structuralcharacteristics of the lamp such as reflector curvature, frontal area,and depth as well as the location of the filament with respect to thereflector. As a general statement, the efficiency is proportional to thetotal solid angle subtended by the reflector surface as referenced tothe light source. Moreover, for a given reflector volume the efficiencyis dependent on the reflector shape or curvature which also influencesthe quality of the projected beam. Thus, spherical surfaces, whilehaving an excellent light collecting efficiency, provide little controlover the reflected beam. Parabolic surfaces provide slightly greaterbeam control but have a lower light collecting efficiency thanthe'spherical surfaces. Paraboloidal surfaces, on the other hand, yieldhigh collecting efficiencies and directional beam control and, for thisreason, have found the greatest acceptance as reflecting surfaces forprojected beam lamps.

The optical performance for a paraboloidal reflector is, to a largeextent, determined by the position of the filament and the overall sizeand focal'length of the reflector. The efficiency as calculatedbyconventional means, however, is merely an approximation inasmuch as thefilament normally has a finite length and cannot be accurately locatedat the reflector focal point. For this reason, the efficiency of atypical commercial lighting unit may be considerably below thecalculated value. Additionally, the optical performance of aparaboloidal surface for a given focal length and reflector depth isgreatly influenced by frontal configuration. By way of example, a rightcircular section will produce the maximum collection efficiency withalterations of the configuration, particularly from intentionallynoncircular frontal profiles, markedly reducing the reflectorefficiency. While the resultant loss can be partially recovered byincreasing the operating temperature and hence the illumination from thefilament, these required compensating manipulations present a definitehindrance to the development of noncircular high performance lamps.

The overall quality of the projected beam from the lamp assembly isfurther affected by the optical characteristics of the lens used toimpart directional control to the reflected beam. More specifically, thelens is typically comprised of numerous optical bodies which refract theincident light to produce an undesirable scattering or glare. Generally,this type of glare is associated with the juncture between the adjacentoptical bodies in the lamp lens. The two edges produced during the lensmanufacture have radii which uncontrollably scatter illuminationthroughout the lens thereby producing glare and, additionally, reducingthe output efficiency of the lamp assembly.

Accordingly, an object of the present invention is to i provide areflector having a discretely faceted surface which produces a projectedbeam of predetermined intensity distribution.

Another object of the present invention is to provide a reflector havinga flexible frontal configuration without an accompanying impairment ofoptical performance.

Another object of the present invention is to provide a lamp wherein theoptics are placed entirely on the lamp reflector so as to project a beamoutwardly of the lamp in a desired illumination pattern.

Yet another object of the present invention is to provide a method ofmaking a reflector having a predetermined frontal configuration anddepth which produces a desired projected light pattern.

A further object of the present invention is to provide a lamp assemblywherein glare is significantly reduced by providing a plurality ofselectively oriented facets on the reflectors, the junctures of whichare shadowed from the light source to reduce uncontrolled reflectingillumination.

Still another object of the present invention is to produce an improvedlighting unit having better pattern control and sharper cut-offs byincorporating beam control entirely on a first optical surface.

Generally, the above objects are accomplished by providing a reflectorof predetermined frontal area and depth with a plurality of discretereflecting facets. Each facet is individually oriented with respect tothe light source so as to project an undistorted reflection of thelatter in a' prescribed direction. The superposition of the individualreflections is then utilized to produce a given illumination pattern. Bycombining a sufficient number of reflector facets of the proper size,shape, and orientation, a composite intensity contour can be synthesizedwithin prescribed limits. Such a reflector can incorporate a number ofgeometrical surfaces. For

example, paraboloidal sections, circular cylinders, or

parabolic cylinder, or a combination thereof may be individually orcollectively used to best synthesize the desired pattern. Afterselection of the facet curvature necessary to fulfill the desiredoptical prescription, the

- facets are arrayed with respect to adjacent facets and FIG. 1 is afront perspective view of a motor vehicle having a lighting systemincluding a cornering lamp made in accordance with the presentinvention;

FIG. 2 is an enlarged view taken along line. 2-2 of FIG. 1;

FIG. 3 is a view taken along line 33 of FIG. 2;

FIG. 4 is a two dimensional intensity contour of the illuminationpattern for the cornering lamp;

FIG. 5 is a three dimensional intensity contour of the illuminationpattern shown in FIG. 4;

FIG. 6 is a view taken along line 6--6 of FIG. 1;

FIG. 7 is a schematic view illustrating horizontal image spread-of afacet reflecting surface;

FIG. 8'is a schematic view illustrating vertical image spread of a facetreflecting surface;

FIG. 9 is a schematic view illustrating the circular approximation of aparabolic surface;

FIG. 10 is a schematic view illustrating selective angular positioningof the facet reflecting surfaces;

FIG. 1 1 is a horizontal schematic view illustrating initial angularpositioning of the facets;

FIG. 12 is a view similar to FIG. 11' illustrating shadowing ofuncontrolled reflecting surfaces; f I

FIG. 13 is a schematic view illustrating one method of facet rotation;

FIG. 14 isa view similar to FIG. 13 illustrating an alternate method offacet rotation;

FIG. 15 is a view illustrating the glare from a faceted reflector;

FIG. 16 is a view illustrating the glare from a lens;

FIG. 17 is a view illustrating the effect of the facet angle on thefocal length position;

FIG. 18 is a top view of a facet die segment;

FIG. 19 is the side view of the die segment of FIG. 18; and

FIG. 20 is the front view of the die segment of FIG. 18.

Referring to FIG. 1, there is shown a motor vehicle 10 having a lightingsystem including headlamps 12, combination turn signal and parking lamps14, and cornering lamps 16. All of the lamps are symmetrically disposedon opposite sides of a longitudinal vehicle axis 18. Each of theaforementioned lamps -is designed to project the illumination outwardlyof the vehicle into a predetermined illumination pattern as prescribedby applicable standards. Thus, the headlamps 12 are used as a majorlighting device to provide general illumination ahead of the vehicleduring driving conditions of reduced visibility. The turn signal lamps14 flash in unison with corresponding rear lamps to indicate theintention of the vehiclev to change direction toward the side on whichthe signal lamp is flashing. The parking lamps 14 on both sides of thevehicle are simultaneously steadily energized to indicate the overallwidth and length of the motor vehicle. The cornering lamps 16 areselectively steadily burning lamps used in conjunction with the turnsignal system to supplement the head lamps 12 by providing additionalillumination in the direction of a contemplated turn.

Referring to FIGS. 2, 3, and 6, the cornering lamps 16 are mounted in anopening 20 formed in the side of the vehicleat the lower forward portionof the vehicle front fender 22. Each lamp 16 generally comprises areflector 24, a light source 26 carried by the reflector 24, and a lens28, the outer periphery of which is 24 includes a peripheral groove 30which retains a resilient gasket 32. The lens 28 includes a rearwardlyprojecting marginal lip 34 that engages the gasket 32 to form a sealedenvelope 36 defined by the interior surfaces of the lens 28 and thereflector 24.

The lens 28 includes a marginal flange 38 on which a second resilientgasket 40 is positioned. The cornering lamp 16 is positioned at theopening 20 with an inwardly turned edge of the latter resilientlyengaging the gasket 40. The cornering lamp 16 is then fixedly secured inthis position by fasteners 42 which clamp outwardly projecting mountingears 44 at the sides of the reflector 24 to spaced brackets 46 fixed tothe interior surface of the front fender 22.

The lens 28 is formed of a light transmissive material such as plasticand has a clear front window 48. When used with the subject facetedreflector, the lens 28 may be optically passive and require none ofcorrective optical means conventionally used on lamp lenses. However,the window 48 may include optical flutes or prisms for additionallydistributing the illumination controlled by the reflector 24, if thesame are deemed desirable.

The light source 26 is horizontally and vertically centered with respectto the reflector 24 and generally includes a socket 50 and a lamp 52having a helically coiled filament 54. The socket 50 includes a pair ofleads 56 which are electrically connected to a power supply (not shown)such as the vehicle battery for energizing the filament 54. While thelight source 26 may take various forms depending on the type of lightingunit in which it is. incorporated, appropriate means should be providedfor accurately locating the filament 54, in assembly, with respect tothe hereinafter described faceted surface of the reflector 24.

The reflector 24 includes a dish-shaped base section 58 having a frontfaceted surface, generally indicated by reference numeral 60, which issuitably coated or otherwise prepared to intercept and reflect lightemitted from the filament 54. More specifically, the faceted surface 60may be aluminized, silvered, or metallically coated as by chromedeposition to provide the aforementioned reflecting capabilities.

The faceted surface 60 is defined by a plurality of individuallyoriented discrete facets which will be, for purposes of description,hereinafter designated by subscripts depending on their position withrespect to the filament 54. Thus, as shown in FIG. 3, the facetedsurface 60 is horizontally divided into three rows, a middle row bearingthe subscript M, an upper row bearing the subscript U, and a lower rowbearing subscript D. The

faceted surface 60 is vertically divided into seven columns, the middlecolumn being designated 1 with adjacent rows on the left beingsuccessively designated as 2L, 3L, and 4L and adjacent rows on the rightbeing More specifically, all facets are deliberately positioned behindthe light source 26 so as to reflect an image of the filament 54. Inthis manner, the,illumination pattern produced by the complete reflectoris the sum or superposition of all the individual images. The particularcontribution of the individual facet is determined by its projectedpattern which has characteristics dependent on its shape and locationwith respect to the light source 26. By combining facets in a sufficientnumber of the proper size, shape, and orientation, the contemplatedillumination pattern can be accurately synthesized.

Experience, in this respect, has indicated that the intensity patternfor a cornering lamp should provide a wide illumination pattern in ahorizontal plane and a relatively narrow or concentrated pattern in avertical plane. Accordingly, to most conveniently accomplish thisresult, the major axis 70 of the lamp 16 is horizontally disposed at asuitable angle to the longitudinal vehicle axis 18 and the minor axis 72is vertical and mutually perpendicular to the major axis 70 and vehicleaxis 18.

The intensity or isocandle contour for the cornering lamp 16 positionedon the right side of the vehicle is shown in FIGS. 4 and 5 wherein ahigh or peak intensity zone 80 is established slightly below the majoraxis 70 of the lamp and angularly displaced with respect to thelongitudinal vehicle axis 18. The high intensity zone 80 iscircumscribed by zones of decreasing intensity, designated successively82, 84, 86, and 88. For purposes of future reference, the nine hundredcandlepower (cp) peak intensity zone 80 positioned at 35 from thelongitudinal vehicle axis 18 and below the lamp major axis 70. The lamp16, as referenced to the vehicle longitudinal axis 18, has a reflectoraxis 120 angularly displaced 45 outwardly and 2.5 downwardly. The centerof the overall intensity pattern is determined by the 0 to 100 cp slicepattern which has a relatively narrow vertical spread V and relativelylarge horizontal spread H. More particularly, in the preferredembodiment, the horizontal spread H is approximately 50 and subtends thesector from 20 to 70. The vertical spread V is approximately 5 andextends downwardly 5 from the horizontal lamp major axis 70.

The cornering lamp 16, as previously mentioned, includes a plurality ofindividually oriented facets which accurately synthesize theabove-described illumination pattern within prescribed limits. The exactsize, curvature, and orientation of the individual facets is determinedby a number of design requirements, foremost of which are the resultantlight pattern; the peripheral configuration of the reflector; the depthinto which the reflector must fit; the filament configuration; theposition of the filament with respect to the reflector; and thetemperature profile of the filament.

With the wide horizontal and narrow vertical spreads required incornering lamps, a filament positioned with its longitudinal axis in ahorizontal plane in combination with reflector facets which areparabolic or circular cylinders having axes parallel to the horizontalplane has been found to provide the most satisfactory results.

The peripheral configuration and depth of the reflector is norinallydetermined in advance by styling and other design configurations. Assuch, the basic size of the lamp reflector will be subjectivelyinfluenced by aesthetics, the required intensity profile, and thepractical limits of reflector efficiency and focal length. Inasmuch aslamps with a collection efficiency of less than 30 percent provideunacceptably low performance, this figure will specify a reflectorheight once the width and focal length of the reflector are given. Thewidth is usually prescribed by the styling aesthetics insofar as thesame is compatible with the practical performance limits.

Regardless of the many considerations noted above, the hereinafterdescribed method of synthesizing a desired illumination patternrestricts the actual reflector size only to the extent that the requiredprecision of the final pattern necessarily controls the number of facetsand their accompanying reflector area. The reflector form also, to alarge extent, determines the location of the filament and generallyestablishes the size of the central facet which constitutes the basicbuilding block in determining the boundaries of the desired illuminationpattern. The focal length of this central facet will hereinafter beregarded as the focal length of the reflector.

Other criteria for effecting initial design of the reflector are thefilament candlepower required to supply the energy for the illuminationpattern and the practicability of placing the filament at the focalpoint of the reflecting surface. Generally, this last criterionestablishes a minimum focal length of about one inch for motor vehiclelamps. Insofar as the filament energy output is concerned, the operatingtemperature and lifetime requirements of tungsten filaments require acylindrical helically wound configuration which satisfies the specifiedcandlepower requirements.

Once the focal length is set, the depth is detennined from the buildupof the facets. In this respect, the depth can be approximated bycomputing the depth for a paraboloid of a given frontal area having thesame focal length as the faceted reflector. Alternately, the depth canbe specified within the limits and the facets designed to fit within thethus prescribed frontal area and depth. This last method of building upthe pattern is the most confining, of course, and may produce the leastdesirable fit of the desired pattern.

' The exact number of facets chosen for a given reflector depends uponthe permissible size of the reflector, the shape of the desiredintensity pattern, and the precision to which the pattern must befitted. The size of the facets, in turn, is determined by the size ofthe desired intensity pattern. The shape and orientation of the facetsare primarily controlled by the relative position of the variousintensity zones within the overall iland the reflecting surface 102, aswell as the overall length and configuration of the filament 104. Thereflecting surface 102 will produce vertical image spread Y, the valueof which is determined by the subtended angle (1) of the surface 102with respect to filament 104, the distance between the reflectingsurface 102 and the filament 104, the curvature of the reflectingsurface 102, and the diameter of the filament 104. The samerelationships generally hold true for the other contemplated reflectingsurfaces such as paraboloidal, spherical, cylindrical, or elliptical.

With the above guidelines, the optical prescription for the lamp 16proceeds by dividing the idealized illumination pattern in constantintensity regions, as shown in FIGS. 4 and 5, and thereafter matchingthe shape and intensity of the images from the several facets withspecific regions of the pattern following .two criteria insofar as theshape of each individual facet pattern is concerned. First, the totalspread of the image with an individual facet should not exceed eitherhorizontal spread H or the vertical spread V of the desired resultantpattern. Second, the illumination from each facet must be directedtoward an appropriate position in the resultant pattern.

In particular, the prescription for the subject comering lamp pattern isestablished by initially prescribing the central column of facets 1M,1U, and 1D. Inasmuch as this central column is virtually unrestrainedinsofar as width and orientation are concerned and need only satisfy thefirst-mentioned criteria, their facets are, forconvenience, providedwith cylindrical reflecting surfaces having axes parallel to the axis ofthe filament 54. The central facet 1M represents the basic facet in thesynthesis of the reflector and is selected to produce an image as wideand as high as the lowest considered intensity zone. .In the presentinstance, this zone}. is the 100 cp. slice of the resultant beam and isapproximately 50 by 5. The sizing and placement of this facet is mosteasily fulfilled by using a circular cylinder having its focal lengthcoaxial with the filament 54. As shown in FIG. 1 l, the perpendicularbisector of the center or primary facet 1M is colinear with the actuallamp axis 120. Thisorientation directs the illumination toward thegeometrical center of the intensity pattern, 45 horizontal and 2.5 downvertical (FIG. 5).

With the width and height of the basic facet thus determined, the sizesof the upper and lower facets, 1U and ID, are established. Forconvenience of manufacture, the width of these facets is selected to bethe same as the widthof the basic facet 1M. However,the height of thesefacets will generally be less than the height of the center facet.Accordingly, the facets will produce an image as wide as the 100 cp.pattern but with a considerably narrower vertical band.

Because of the ability of the parabola to project a confined beam thefacets 1U and ID are most suitably parabolic cylinders having thefilament 54 at their respective focallengths. However, in order tosimplify construction, inasmuch as a parabolic cylindrical surface isconsiderably more difficult to manufacture than the circular cylindricalsurface, the present invention uses a circular approximation of thesesurfaces. By way of example, the radius of an approximating circularsurface can be represented in the following manner taken with referenceto FIG. 9 wherein a parabolic surface 122 having a focal length P isapproximated by a circular surface 124 having radius R and a center C at(Yo, according to the formulas:

The shape of the circle thus generated matches the parabola at the point(Y,Z) 126 which is taken at the vertical midpoint, (Y, Y )/2 of thesurface. Of course, the degree of approximation diminishes as thedistance from point 126 increases. Therefore, the focal point 132 andcenter of curvature of the circular cylinders are not necessarily in theplane of the filament 54 which is still located at the focal length P ofthe original parabolic surface 122.

The remaining vertical height of the reflector in the center column isevenly divided between the upper and lower facets 1U and 1D. The imagesof these facets are directed'toward the most intense vertical region,2.5 down, of the pattern with the center of the facet image centered onthe axis 120. The center column of facets thus establishes the lowestintensity region of the desired pattern and partially contributes to theremaining regions. Thereafter, buildup of the reflector proceedsoutwardly from the vertical edges of the center column facets.

The length and height of each facet in the M or middle horizontal row isgoverned by the length and height of that intensity slice of the totalpattern which the facet image is attempting to match. For example, theconstant intensity slice 300 cp., FIG. 4, has a horizontal spread ofabout 40 and a vertical spread of approximately 4 with a and centers at40 horizontal. Thus, as shown in FIG. 11, the 2M facets are directedtoward I 40 horizontal with sufficient width for a 40 horizontal spread.

For the initial synthesis, the vertical edges of adjacent facets shouldbe continuous in order to most efficiently utilize the predeterminedreflector volume to best initially synthesize the desired pattern. Theremaining middle facets are directed toward the peak intensity region ofthe total pattern 35 horizontal (FIG. 11). Representatively, as shown inFIG. 10, these two requirements orient the 2LM facet or surface at anangle 6 with respect to the basic facet IM or line 152 with the facetsbeing commonly joined at vertical edge 154. Insofar as the middle row offacets is concerned, the angle is referred to the plane of the basicfacet 1M at the horizontal center line of the lamp. The angle 0, foreach facet is determined byv solution of the following equation:

tan (20 (a+ L)/(PL tan 6,)

For each of these facets, theradius of curvature, r,,, is I equal totwice the distance between the line 152 which comprises the cylindricalsurface in the horizontal plane and a second line 158 through the centerof the filament 54 parallel to and in the same plane as the first line,or r 2P for facet 1M.

. Referring to FIG. 11, the 4RM facet includes a line 160 comprising thecylindrical surface of the facet in the central horizontal plane. Asecond line 162 passes through the center 164 of the filament 54 and isparallel toand lies in the same plane as line 160. This spacingestablishes a D-value or distance D between the lines 160 and 162 whichis one-half the radius of curvature, r of the facet 4RM. The D-values"for the remaining facets in the middle row M are established in asimilar manner. For the upper rows U and lower rows D, the facets arecircular cylinders which approximate parabolic cylinders in theabove-described manner. The focal length P of the initially paraboliccylinder is the D-value of the middle facet in the corresponding column.However, as previously mentioned, when the parabolic cylinder isestablished, the focal point and the center of curvature of theresulting circular cylinders are not necessarily in the horizontalplane.

The upper or lower facets in a given column are, to a large extent,dependent on the size and position of the middle facet. Morespecifically, in as much as both the middle row of facets and the totallamp height are symmetrical about the horizontal lamp axis, the heightof the upper facets, for instance, is the distance between the upperedge of facet 2RM and the upper vertical edge of the reflector. Thewidth and angle 0, with respect to the axis of the filament 54 is thesame as for the middle facet to minimize boundary gaps. This process isapplicable to all the rows and columns of facets to complete initialsynthesization of the desired pattern. The pattern thus prescribed, inmany instances, provides an acceptable optical performance for thereflector. However, further precision and refinement of the basicreflector surface can be achieved by selectively reorienting theseparate facets.

While many repositioning techniques can be used to improve the opticalperformance of the reflector, the two methods described belowsignificantly improve the illumination pattern while minimizing therequired facet movement. In one method, as shown in FIG. 14, arepresentative fac-et 170 as referenced at the geometrical center of thereflecting surface 172 is universally rotated about the focal axis 174.Alternately, the facet 170 is rotated about a horizontal axis 176passing through the center 177 of its reflecting surface 178 to producea vertical shift of the image and about a vertical axis 179 passingthrough the center 177 to produce horizontal shift of the image.Inasmuch as the latter method generally requires a lesser repositioningof the individual facets to achieve a given improvement in the overallillumination pattern, this method will be hereinafter described.

The aforementioned rotation of the element 170 about its geometricalcenter causes the focal length of the surface to retreat from a linethrough the center of the filament 54 thereby distorting the reflectedimage of the latter. With each incremental shift, the image projected bythe reflecting surface will become increasingly distorted. Thus, at somepredetermined point, which we have determined to be about 4 percent ofthe focal length, an unacceptably distorted image will be produced.Therefore, if the shift of the image is greater than this value, arevised facet angle 0 and a new radius of curvature r for the facet mustbe established so that the reflected image is once again withinprescribed limits of distortion and directed toward the intendedposition in the illumination pattern.

For example, as shown in FIG. 17, a facet 180 has an original facetangle 0 with respect to the axis 182 of the filament 54 and a D-value, Das established between a line 184 through the center of the filament 54and a parallel line along the reflecting facet 180. As the surface 180is rotated about its center 188 through an angle (2, to a rotatedposition 190, the line 192 parallel to the surface 190 placed at theoriginal D- value is shifted an incremental distance d from the centerof the filament 54. To compensate for this displacement, the radius ofcurvature of the facet is appropriately changed to establish a revisedfacet D- value, D By way of example, if the original radius and thefacet angle 6 for the 2RM facet are 3.065 in. and 54 40, and the imageis to be shifted 10 toward the car axis in the horizontal plane, thefacet is rotated 5 about the center of its surface to effect thisrequired shift. However, this movement causes a 0.100 in. inward shiftof the facet focal length thereby producing a distorted image. Thismovement exceeds the aforementioned 4 percent for an undistorted imageinasmuch as:

shift/focal length 0. /1 .5 6.7%

This 10 image shift can be accomplished while maintaining the filamenton focus by recomputing the facet prescription to a radius of 3.268 anda facet angle of 6132'A.

By either of the above rotational methods, the marginal edges retreat oradvance with respect to the edges of adjacent facets. Referring to FIG.12, the boundary discontinuities between adjacent facets shown in solidlines produces uncontrolled reflecting surfaces 206 and shadowedreflecting surfaces 208. The surfaces 206 are exposed to the thefilament 54 and because they have indiscriminate shapes and positions,scatter the intercepted light thereby causing glare. On the other hand,the surfaces 208 are not exposed to the light and, accordingly, do notpresent a glare problem.

For the molded lamp components, a minimum draft angle must be providedat the juncture between the facets in order to permit the release of thearticle from the mold. A conventional lens, as shown in FIG. 16, havingoptical flutes 209 or the like formed on an interior surface producesuncontrolled surfaces 210 between exposed edges 212 and 214 produced bythe draft anglerll At each of these edges, the light will beuncontrollably reflected and refracted. However, for the facet reflectorshown in FIG. 15, the required draft angle 41,; produces releasable,conical surfaces 220 and permits location of adjacent facets such thatonly one edge 222 is exposed to the light from the filament. The otherradius 224 is hidden from the filament and, therefore, does notcontribute to glare.

Referring to FIG. 12, for an arbitrary diepull angle Z between reflectorand the lamp axis and the pull line 230, the uncontrolled surfaces 206are not deliberately positioned with respect to the filament and thusrandomly distribute or scatter illumination. The glare caused by suchsurfaces is obviated in the present invention by shifting the outwardfacets rearwardly facet angle is then recalculated .to redirect an.undistorted image toward the intended position in the intensity pattern.

When the above operations have been completed, the same is translatedinto numerical form for construction of a die from which the desiredreflectors can be manufactured by conventional forming processes. Eachfacet, as shown in FIGS. 18 through 20, will be produced by a diesegment 240 having a reflecting surface 242 with a profile width A and aprofile height B. The reflecting surface 242 will have a radius R withorigin axis 244 displaced a distance Q from the center axis 246 of thesegment 240. The surface normal 247 between the reflecting surface 242and the axis 246 is inclined at an angle a. The center of the reflectingsurface 242 will be displaced a distance I from rear face 250 of thesegment 240. The axis 244 is then displaced a distance 2 in thehorizontal plane as measured from a reference pin 252 aligned with theaxis 246 and having a 0.250 in. diameter. As designated in theaforementioned manner, a lamp assembly having a frontal profile of 2.50in. X 5.00 in. and a central facet focal length of 1 inch wassuccessfully manufactured to produce a resultant light pattern as shownin FIGS. 4 and 5 using the following dimensions.

facet A B Sina Z R 0 0.625 1.250 0.0218 3.250 2.000 0.021 Right 1U 1.6250.625 0.l062 3.903 2.694 1.138 Left 10 0.625 0.625 0.1062 3.901 2.6941.144 Right 0.688 1.000 -0.27l2 3.413 2.097 0.019 Right 0.688 0.750-0.-3720 3.903 2.666 1.040 Left 0.688 0.750 0.3788 3.920 2.666 0.988Right 0.688 1.000 0.2506 3.378 2.090 0.015 Left 2RU 0.688 0.750 0.21973.942 2.663 1.020 Right 2Rd 0.688 0.750 -0.2346 3.939 2.663 1.015 Left0.750 1.000 0.6l55 3.839 2.440 0.019 Right 0.750 0.750 -0.6473 4.2602.925 0.983 Left 0.750 0.750 0.6481 4.269 2.925 0.054 Ri'ght 0.7501.000v 0.36574 3.748 2.296 0.034 Right 0.750 0.750 0.3746 4.362 2.9011.048 Right 0.750 0.750 0.3926 4.359 2.901 1.020 Left 0.750 1.000-0.8l61 4.556 3.065 0.047 Right 0.750 0.750 -0.8l89 4.919 3.447 0.983Left 0.750 0.750 0.8179 4.946 2.447 0.900 Right 0.750 1.000 0.5033 4.3742.706 0.019 Left 0.750 0.750 0.5253 4.785 3.130 0.923 Right 0.750 0.750-0.5249 4.769 3.130 0.973 Left The instruction left or right in the lastcolumn of the table refers to the direction of the center of the radius244 from the facet centerline 246 (distance Q) as viewed in FIG. 19.

Although only one form of this invention has been shown and described,other forms will be readily apparent to those skilled in the art.Therefore, it is not intended to limit the scope of this invention bythe embodiment selected for the purpose of this disclosure but only bythe claims which follow.

What is claimed is:

1. A reflector for projecting light from a source in a predeterminedillumination pattern, said' reflector comprising: a plurality ofdiscrete reflecting facets; light focusing reflecting surfaces on saidreflectingfacets, each of said reflecting surfaces having curvaturesindividually focused with respect to the source to project anundistorted image of the source, said reflecting surfaces havingreflecting areas projecting individual images with a given horizontaland vertical image spread and intensity, said reflecting surfacesfurther being spacially located with respect to the source to directsaid images toward select portions of the desired illumination patternsuch that the superposition of said individual images synthesizes thepattern within said prescribed limits, a portion of said reflectingsurfaces being in the form of right circular cylinders having curvaturesapproximating parabolic cylinders which are focused with respect to thesource.

2. A faceted reflector for projecting light from a source in apredetermined horizontal and vertical illumination pattern, saidreflector comprising: a plurality of discrete and contiguous reflectingfacets; light focusing reflecting surfaces on the facets havinguncontrolled light diffusing surfaces between contiguous facets, saidreflecting surfaces having reflecting areas for projecting images withdesired horizontal and vertical spreads and projected intensities, saidreflecting surfaces further being focused with respect to the source forprojecting glare free undistorted images of the latter and beingspacially located with respect to the source to direct said undistortedimages toward select portions of said illumination pattern such that thesuperposition of the projected undistorted images synthesizes thepattern, the facets being further positioned with respect to adjacentfacets so as to shade said uncontrolled light diffusing surfaces fromsaid source thereby further reducingglare due to scattered reflection.

3. A lighting unit having optics entirely on a reflecting surface fordistributing light in a desired illumination pattern, comprising: anoptically passive lens; a reflector, said lens and said reflector havingfacing interior surfaces defining a lamp envelope; a light sourcepositioned in the envelope; a plurality of facets on said reflector;cylindrical light focusing reflecting surfaces on said facets, saidreflecting surfaces being interconnected by uncontrolled reflectingsurfaces, said light focusing reflecting surfaces having a shape andcurvature for intercepting illumination from the source and reflectingthe latter with a given image spread and intensity outwardly throughsaid optically passive lens toward select portions of said illuminationpattern, the position and shape of the individual facets beinginterrelated so as to focus the facets with respect to the source toproject glare free undistorted images thereof and being additionallypositioned such that the image spreads and intensities provide acomposite pattern synthesizing said desired pattern, the individualfacets being further positioned relative to adjacent facets and thelight source so as to shade said uncontrolled reflecting surfaces fromthe light source thereby reducing glare from scattered illumination.

15.; 4. A motor vehicle lamp having optics placed entirely on areflecting surface for projecting a light beam in a desiredhorizontaland vertical illumination pattern,

comprising: a lens having an optically passive light transmittingregion; a reflector adapted to be mounted on the motor vehicle andcooperating with the lens to form a lamp envelope; a light sourcepositioned within said lamp envelope; a faceted surface-0n saidreflector including horizontal rows andvertical columns of discretefacets, said faceted surface having sufficient area to projectillumination of requisite intensity throughout the contemplated pattern,said facets being interconnected by uncontrolled glare producingreflecting surfaces, said facets having right cylindrical reflectingsurfaces approximating parabolic cylinders focused with respect to thesource so as to project undistorted images through said lighttransmitting region, each of said facets having a width, height, andcurvature and being positioned relative to the source to distributeillumination with a given spread and intensity toward a select portionof the desired illumination pattern, the facets being interrelated so asto match the overall spread and intensity of the illumination patternwithin prescribed limits, the facets being positioned relative toadjacent facets so as to shade said glare producing reflecting surfacesfrom the light source thereby reducing glare fromuncontrolledreflection.

1. A reflector for projecting light from a source in a predeterminedillumination pattern, said reflector comprising: a plurality of discretereflecting facets; light focusing reflecting surfaces on said reflectingfacets, each of said reflecting surfaces having curvatures individuallyfocused with respect to the source to project an undistorted image ofthe source, said reflecting surfaces having reflecting areas projectingindividual images with a given horizontal and vertical image spread andintensity, said reflecting surfaces further being spacially located withrespect to the source to direct said images toward select portions ofthe desired illumination pattern such that the superposition of saidindividual images synthesizes the pattern within said prescribed limits,a portion of said reflecting surfaces being in the form of rightcircular cylinders having curvatures approximating parabolic cylinderswhich are focused with respect to the source.
 2. A faceted reflector forprojecting light from a source in a predetermined horizontal andvertical illumination pattern, said reflector comprising: a plurality ofdiscrete and contiguous reflecting facets; light focusing reflectingsurfaces on the facets having uncontrolled light diffusing surfacesbetween contiguous facets, said reflecting surfaces having reflectingareas for projecting images with desired horizontal and vertical spreadsand projected intensities, said reflecting surfaces further beingfocused with respect to the source for projecting glare free undistortedimages of the latter and being spacially located with respect to thesource to direct said undistorted images toward select portions of saidillumination pattern such that the superposition of the projectedundistorted images synthesizes the pattern, the facets being furtherpositioned with respect to adjacent facets so as to shade saiduncontrolled light diffusing surfaces from said source thereby furtherreducing glare due to scattered reflection.
 3. A lighting unit havingoptics entirely on a reflecting surface for distributing light in adesired illumination pattern, comprising: an optically passive lens; areflector, said lens and said reflector having facing interior surfacesdefining a lamp envelope; a light source positioned in the envelope; aplurality of facets on said reflector; cylindrical light focusingreflecting surfaces on said facets, said reflecting surfaces beinginterconnected by uncontrolled reflecting surfaces, said light focusingreflecting surfaces having a shape and curvature for interceptingillumination from the source and reflecting the latter with a givenimage spread and intensity outwardly through said optically passive lenstoward select portions of said illumination pattern, the position andshape of the individual facets being interrelated so as to focus thefacets with respect to the source to project glare free undistortedimages thereof and being additionally positioned such that the imagespreads and intensities provide a composite pattern synthesizing saiddesired pattern, the individual facets being further positioned relativeto adjacent facets and the light source so as to shade said uncontrolledreflecting surfaces from the light source thereby reducing glare fromscattered illumination.
 4. A motor vehicle lamp having optics placedentirely on a reflecting surface for projecting a light beam in adesired horizontal and vertical illumination pattern, comprising: a lenshaving an optically passive light transmitting region; a reflectoradapted to be mounted on the motor vehicle and cooperating with the lensto form a lamp envelope; a light source positioned within said lampenvelope; a faceted surface on said reflector including horizontal rowsand vertical columns of discrete facets, said faceted surface havingsufficient area to project illumination of requisite intensitythroughout the contemplated pattern, said facets being interconnected byuncontrolled glare producing reflecting surfaces, said faceTs havingright cylindrical reflecting surfaces approximating parabolic cylindersfocused with respect to the source so as to project undistorted imagesthrough said light transmitting region, each of said facets having awidth, height, and curvature and being positioned relative to the sourceto distribute illumination with a given spread and intensity toward aselect portion of the desired illumination pattern, the facets beinginterrelated so as to match the overall spread and intensity of theillumination pattern within prescribed limits, the facets beingpositioned relative to adjacent facets so as to shade said glareproducing reflecting surfaces from the light source thereby reducingglare from uncontrolled reflection.